Arthropod pests are one of the major threats to human welfare and exert continued stress on the food supply and transmit a broad array of medical and veterinary diseases. Synthetic insecticides played a significant role and in many ways ushered in modern agriculture and pest control. However, the widespread use of synthetic insecticides also created numerous environmental challenges. The acute effects of synthetic pesticides on professional applicators and other end users are well-known but the chronic long term human health effects can be equally serious. Further, the use of synthetic insecticides has led to the development of resistant insect populations. Insecticide resistance is a complex phenomenon underlined by a diverse array of physiological mechanisms. Major mechanisms that are responsible for the development of insecticide resistance are metabolic detoxification, target site mutation, reduced cuticular penetration and behavioral avoidance.
Integrated Pest Management (“IPM”) is a holistic approach to pest management. A fundamental aspect of insecticide utilization under the broader framework of IPM is the management of insecticide resistance (IRM) by the utilization of insecticide combinations that reduce the rate of resistance development. A combination of insecticides with different modes of action is fundamentally a concept based upon the idea of redundant killing of target insects. Insects adapted to one of the active ingredient in the combination product will still be killed by the other active ingredient. Mixtures can also reduce the amount of pesticides applied in the environment and the environmental impact associated with pesticide applications.
Most botanical insecticides are readily biodegradable and significantly less harmful to the environment and users than synthetic insecticides. The very short environmental persistence, usually less than 24 hours, of plant derived insecticides is favorable to the survival of non-target, beneficial parasites and predators which are important components of IPM. Unlike conventional insecticides which are typically based on a single active ingredient, plant derived insecticides usually comprise an array of chemical compounds that affect both behavioral and physiological functions of the target arthropods. The probability of pest resistance developing to plant derived insecticides is less than that for synthetic pesticides because these mixtures may have a variety of modes of action.
One effective naturally derived pesticide is found in the tissues of many of the plants of the genus Schoenocaulon, commonly referred to as sabadilla. The species with the longest history of use, and the most readily available, is Schoenocaulon officinale. The plant is indigenous to Central and South America and its seeds have been used for centuries for their insecticidal properties. The seeds contain several alkaloids including veratridine and cevadine, both of which are known to be active against arthropods.
Bacillus thuringiensis is a natural soil bacterium. Many Bacillus thuringiensis strains produce crystal proteins during sporulation called δ-endotoxins which can be used as biological insecticides. Bacillus thuringiensis produces crystals which paralyze the digestive system of some larvae within minutes. The larvae eventually die of starvation. One advantage of using Bacillus thuringiensis is that they are target specific. They do not harm humans or other non-target species. Yet another advantage of Bacillus thuringiensis is that they can be used on organic crops. Further, with no mandated pre-harvest interval, it can also be used on crops right before harvest.
Bacillus thuringiensis subsp. aizawai is commercially available as XenTari® (available from Valent BioSciences Corporation, XenTari is a registered trademark of Valent BioSciences Corporation). Bacillus thuringiensis subsp. kurstaki is commercially available as Dipel® (available from Valent BioSciences Corporation, Dipel is a registered trademark of Valent BioSciences Corporation). Bacillus thuringiensis subsp. thuringiensis is commercially available as Novodor (available from Valent BioSciences Corporation).
Thus, there is a need in the art for pesticide combinations that contain naturally derived pesticides that decrease health concerns to humans and also decrease the risk of the development of pesticide resistance.